Pressure accumulator and method of forming the same

ABSTRACT

A pressure accumulator and method of forming the same is disclosed which comprises the steps of advancing a cylindrical resilient metallic sleeve carrying a separator or bladder through the open mouth of a shell forming a part of the casing of the accumulator, the shell including on an inner wall surface thereof an annular groove defining an inwardly directed sharpened lip in the casing wall. The sleeve is positioned such that the outer circumference thereof, adjacent its upper end, is disposed in abutting relation to the said lip. An electrode is placed against the upper edge of the sleeve opposite the lip at a position remote from the deformable bladder. The shell section and the electrode are relatively rotated about an axis of revolution coincident with the longitudinal axis of the shell while electrical current is passed through the electrode, sleeve, and into the casing, the current flow being sufficient to induce a melting and consequent fusion between components of the metal forming the sleeve and lip portion, whereby the sleeve is secured to the shell section and a seal is defined by the annular fused portions of the shell and the sleeve. Thereafter the open mouth portions of the shells are welded together to define a completed casing.

This invention relates to the art of pressure vessels and method offorming the same, and more particularly to a pressure accumulator of thetype having a rigid casing with a deformable separator therein in theform of a bladder dividing the vessel into two chambers, one of which ischarged with gas under pressure and the other of which is charged withoil under pressure.

The casings of pressure accumulators of the type described are typicallyfabricated of separate halves or shells having open mouth ends andclosed ends which may be hemispherical. The end portion of one saidshell has mounted therein a fluid port for the admission of oil, whereasthe other end carries a gas charging valve.

In accordance with standard practice, the separator is typically securedto an annular metallic sleeve and may be molded to a portion of thesleeve. The metallic sleeve is thereafter secured within one of theshell halves, as by welding or by some other fastening procedure. Theassembly is completed by connecting the shell halves, as by an annularweld.

Substantial difficulties have been encountered in mounting the sleevecarrying the separator within the shell. The sleeve must be accuratelypositioned and securely fixed against axial movement within the shelland, in addition, the connection must be leakproof to preclude thepassage of fluids around the separator.

In accordance with one method of locating the sleeve, an annular weld isformed between an inner wall portion of the shell and sleeve. Problemshave arisen in the formation of such welds since, unless the weld formsa complete seal, leakage between the sleeve and the inner wall may beexperienced. On the other hand, the substantial heat generated in thecourse of formation of the weld may be transmitted through the casingand sleeve to the separator or bladder, which is typically formed of anelastomeric material and, hence, subject to degradation and destructionby heat.

It is accordingly a principal object of the invention to provide amethod of manufacturing a pressure accumulator device wherein themounting of the bladder retainer sleeve within the casing is simplified,to assure formation of an effective seal while minimizing heattransmission to the elastomeric separator member.

More specifically, it is among the objects of the present invention toprovide a simplified and improved method for attaching a separatorsupport sleeve carrying an elastomeric bladder to an inner wall portionof the casing while minimizing the possibility of damage to theseparator, by forming in the inner wall portion an annular groovedefining an inwardly facing lip. The retainer sleeve end, which isremote from the portions of the sleeve to which the separator isattached, is aligned with the lip, the noted portions being in intimateengagement.

Thereafter, a fused connection is formed between the noted parts bypositioning a welding electrode against the inner circumference of thesleeve, preferably at a corner portion, and causing a welding current toflow through the electrode, sleeve, and to the grounded casing at anarea of relatively small cross section, the welding current beingsufficient to fuse the reduced cross section portion of the sleeve tothe lip and lip-adjacent wall portion. During the flow of weldingcurrent, a relative rotation of the electrode and shell is effectedwhereby the heat generated at any one increment is greatly reduced,minimizing the possibility of damage to the separator.

A further object of the invention lies in the provision of an improvedpressure accumulator device.

According to the invention, these objects are accomplished by thearrangement and combination of elements hereinafter described and moreparticularly recited in the claims.

In the accompanying drawings, in which are shown two of various possibleembodiments of the several features of the invention:

FIG. 1 shows a longitudinal sectional view of a pressure accumulator inaccordance with the invention;

FIG. 2 is a fragmentary sectional view of the components at anintermediate state of assembly;

FIG. 3 is a fragmentary view at a further stage in the assembly;

FIG. 4 is a view similar to FIG. 3 after fusion of the parts;

FIG. 5 is a sectional view of an embodiment at a stage similar to thatof FIG. 3.

Referring now to the drawings, the accumulator 10 comprises a generallycylindrical casing or pressure vessel formed of an upper shell component11 and a lower shell component 12, the shell components being connectedtogether by an annular weld 13. The shell components 11, 12 are formedof rigid material, such as steel, capable of withstanding the highpressures to which the accumulator will be subjected in use.

As is conventional, the accumulator includes a gas charging valve 14extending through a circular aperture 15 in the closed end portion 16 ofthe upper shell 11. The fluid port 17 may include a fitting 18, securedas by weld 19 in an aperture 20 in the closed end 21 of the lower shellsection 12.

The usual deformable bladder or separator 22 of natural or syntheticrubber includes a rigid valve member 23 at the lower end thereof, itbeing understood that the function of the member 23 is to preventextrusion of the bladder through the oil port 17. In the distendedposition of the bladder or partition 22, the valve member 23 seats overthe port to seal the same.

The upper end of the bladder 22 includes a thickened rim 24 which may bemolded over retainer shoulder 25 of the partition retainer sleeve 26.The partition retainer sleeve 26 is preferably formed of a resilientmetallic material compatible with, i.e. fusible to, the metal of thecasing.

The principal advance of the present invention resides in the manner inwhich the sleeve 26 is secured to the shell section 12 to provide therequisite sealing against passage of fluids across the junction ofsleeve and casing, and to prevent axial movement of the sleeve withinthe shell section 12.

The section 12, in an inner wall portion thereof, is formed with anannular groove 27, the configurations of which are best understood froman inspection of the enlarged fragmentary views FIGS. 2, 3 and 5.

The groove 27, which may be triangular in vertical section, includes anupwardly facing shoulder portion 28 and an inclined side wall portion29. The sleeve 26 is positioned by inserting the same through the openmouth 30 of lower shell section 12 and shifting the same downwardlyuntil the upper end 31 of the sleeve is in essentially precise alignmentwith the upwardly facing shoulder portion 28 of the groove 27.

The diameter of the sleeve 26 is calculated to provide an intimateinteference or frictional fit with the interior diameter of the shellsection 12 and is preferably urged into the desired aligned positionshown in FIG. 2 (wherein the sleeve appears in dot and dash lines) by ajig or insertion tool 32.

The tool 32 includes a base portion 33, the radial outermost portions ofwhich engage against the top surface 31 of the sleeve. The tool 32includes an outwardly extending shoulder 34 which, when moveddownwardly, seats against the upper edge 35 of the shell section 12, thespacing between shoulder 34 and base 33 being adjusted preciselyheight-wisely to orient the sleeve 26 in the shell.

After positioning by the tool 32, the parts will have reached theposition shown in FIG. 3.

Connection between the sleeve 26 and shell section 12 is effected by anelectrical fusion process which is well known per se, such processinvolving the passage of high current from electrode 36 which isconnected to the "hot" terminal of a welding transformer, to the casingor shell section 12 connected to the ground terminal of the transformer.

As best seen in FIG. 3, the upper end portion 37 of the sleeve 26preferably includes a square corner 37a against which the lower edge 38of the electrode 36 is pressed. A spring loading action of the electrodein the direction of the axis thereof may be provided to assure outwardflow of the metal.

During the flow of current through the electrode 36, a relative rotationbetween the electrode and shell section 12 is effected, such rotationbeing about an axis coincident with the vertical axis of the shellsection 12. It will be understood that such rotation may be accomplishedby rotating a jig or like support carrying the shell 12 while theelectrode is maintained in fixed position, or by rotating the electrodewith the shell section maintained stationary.

The current flow will result in a progressive melting and fusion of themetal portions, particularly the upper end portion 37 engaged by theelectrode and the adjacent inner edge 40 of shoulder 28, such reducedend portion 37 and edge 40 being the components of highest resistance inthe electrical circuit and, hence, the area of principal voltage dropand heat concentration.

Following relative rotation of the electrode and shell section 12, afused connection will be developed between the sleeve 26 and wallportions within groove 27, substantially as represented, by way ofexample, in FIG. 4.

The amount of current flow and speed of rotation must be tailored to therequirements of the particular embodiment, being varied in accordancewith such factors as thickness of material, composition of material,etc., optimal conditions being readily determined.

Due to the concentration of heat in a limited area, as hereinabove setforth, and the constant rotation of the components, plus the fact thatthe thicker shell section 12 acts in the manner of a heat sink, the heattransmitted downwardly through sleeve 26 to the partition isinsufficient to damage the elastomeric partition. As shown in thedrawings, and particularly FIGS. 1 and 3, there is metal to metalcontact between the cylindrical side portions 26a of sleeve 26 and theinner wall of shell 12 over a substantial area, thereby augmenting thedissipation of heat.

Following fusion, the material of the sleeve 26 defined at the junctionof the upper end of sleeve 26 and the innermost radial portion 40 of theshoulder 28 will have become integrated, essentially as shown at 39 inFIG. 4. The fusion line or area 39 provides a continuous annular sealwhile at the same time securely locking the sleeve against axialshifting movement relative to the shell section 12.

In the embodiment of FIG. 5, wherein like parts have been given likereference numerals, the components are essentially the same asdescribed, except that the spring sleeve 26' is provided with a radiallyoutwardly extending ledge 41 which is inwardly deflected in the courseof insertion and which hooks over the shoulder 28 when the ledge isbrought into registry with groove 27 to facilitate location of thesleeve 26' relative to the shell section 12. The positioning of thesleeve 26', by reason of the automatic locating feature, may be manuallyeffected or may be effected through the use of a tool, such as the tool32.

A pressure accumulator having the structural characteristics hereinaboveset forth and fabricated in accordance with the method described isparticularly suited to automated manufacture, resulting in reducedfabrication costs. In addition, the possibility of overheating andconsequent failure of the bladder is minimized.

As noted, after the sleeve 26 and attached portion 22 have beenassembled, the final weld 13 between the shell sections 11 and 12 iseffected to complete formation of the pressure resistant casing.

It will be readily recognized that variations of the above methods andapparatus may occur to those skilled in the art in the light of theteachings hereof. Accordingly, the invention is to be broadly construedwithin the scope of the appended claims.

Having thus described the invention and illustrated its use, what isclaimed as new and is desired to be secured by Letters Patent is:
 1. Apressure accumulator device including first and second shell members,circular in section, each said shell member including an open mouthportion and a closed end portion, a gas charging valve in the endportion of said first member communicating with a gas chamber, a fluidport in the closed end of said second shell member communicating with afluid chamber, said chambers being separated by an elastomeric bladdermeans, the open mouth portions of said shell members being weldedtogether under heat to define a sealed casing, said accumulator beingcharacterized by its adaptability of assembly without said heatadversely affecting said bladder and wherein one of said shell membersincluding in an inner wall surface thereof an integral annular groovehaving one wall thereof defining a radially extending shoulder disposedin a plane normal to the longitudinal axis of said casing, an axiallyelongated cylindrical bladder retainer sleeve member mounted within saidone section, said bladder means being permanently bonded to a lower endportion of said sleeve member in spaced relation to said shoulder, saidsleeve member including a circular upper end portion disposed inregistry with said shoulder and a continuous fused weld area defining aconnection between said wall portion and said upper end portion of saidsleeve, said connection securing said sleeve against axial movementwithin said casing and defining an fluid-tight seal between said sleeveand said one shell section, said sleeve, in the area between said upperend and said retainer, including annular portions intimately engagedagainst adjacent inner wall portions of said shell whereby heatgenerated in the formation of said fused weld area is conducted into thebody of said shell which serves as a heat sink and away from said bondedconnection of said bladder and sleeve.
 2. An accumulator device inaccordance with claim 1 wherein said end portion of said sleeve includesa radially directed annular shoulder portion extending into said groove.